1. Field of the Invention
The invention relates to an optical engine for a projection display device, more particularly to an optical engine which has fewer components and lower manufacturing costs.
2. Description of the Related Art
As shown in FIG. 1 and FIG. 2, a conventional optical engine 1 for a projection display device usually includes a light source module 11 for providing light, a housing 12 disposed at one side of the light source module 11, an imaging unit 13 disposed in the housing 12, and a projecting mechanism 14 disposed on the housing 12. The housing 12 includes a first housing part 121 and a second housing part 122 for covering the first housing part 121. The first housing part 121 defines a receiving space 123 for receiving a display element 132 and an optical lens set 131 of the imaging unit 13. The second housing part 122 covers the receiving space 123 by covering the first housing part 121 in an overlapping manner. The second housing part 122 is fastened to the first housing part 121.
The projecting mechanism 14 includes a lens barrel 141, a projecting lens 142, and a coupling element 143. One end of the lens barrel 141 extends through an opening 124 of the second housing part 122. The other end of the lens barrel 141 is for mounting the projecting lens 142 thereon. The coupling element 143 is formed on an outer surface of the lens barrel 141, and is fastened to the second housing part 122. A dust-proofing washer 15 made of rubber is disposed between the coupling element 143 and the second housing part 122, and is used to block entry of dust or other contaminants into the receiving space 123 through the opening 124 of the second housing part 122. The receiving space 123 is thus sealed so that dust or other contaminants are prevented from accumulating on the display element 132 and the optical lens set 131. Accordingly, dust or other contaminants are prevented from affecting display quality when images are magnified during image projection.
When the coupling element 143 of the projecting mechanism 14 and the second housing part 122 of the housing 12 are coupled to each other, the dust-proofing washer 15 is needed to meet air-tight and dust-proof requirements between the second housing part 122 and the coupling element 143. Therefore, during manufacture, use of the dust-proofing washer 15 results in extra design burden and additional manufacturing costs. Moreover, since the lens barrel 141 of the projecting mechanism 14 and the second housing part 122 are two separate components, separate molds are required for injection molding, which complicates component design and further increases manufacturing costs. Therefore, it is desirable to improve the design of the conventional optical engine 1 so as to reduce both the number of components and manufacturing costs.